1. Field of the Invention
The present invention relates to a cleaning sheet for a fuser member, such as a fuser roll, a cleaning sheet supplier for a fuser member, such as a fuser roll, and a cleaning apparatus for a fuser member, such as a fuser roll.
2. Description of the Related Art
In electronic photography apparatuses, such as copying machines, laser beam printers, or facsimiles, hitherto, a printing sheet, such as a paper or a film, carrying thereon an unfixed toner image was supplied between a fuser roll and a pressing roll, and the image was fixed on a surface of the printing sheet by the functions of heat and pressure. Therefore, a problem arose in that the toner was transferred to surfaces of the fuser roll and/or the pressing roll, the transferred toner was re-transferred to a rear end of the printing sheet or a next printing sheet, and thus the printing sheet was stained with the toner, that is, a problem of off-set. To avoid such a problem, the fuser roll is coated with an oil to enhance the release properties of the toner transferred on the surface of the fuser roll, and the toner is removed with a cleaning sheet.
The fixing mechanism of a toner image will be explained, referring to FIG. 1, a sectional view schematically illustrating a fixing apparatus. A printing sheet 3 carrying an unfixed toner image 3a thereon is supplied between a fuser roll 1 and a pressing roll 2. When the printing sheet 3 is passed through the fuser roll 1 rotating in a direction of the arrow A shown in FIG. 1 and the pressing roll 2 rotating in a direction of the arrow B shown in FIG. 1, the unfixed toner image 3a is fixed on the printing sheet 3 by heat and pressure. Then, the printing sheet 31 carrying the fixed toner image 3b thereon is moved in a direction of the arrow C shown in FIG. 1.
Further, the fuser roll 1, before coming into contact with the printing sheet 3, is coated with an oil 4a supplied from an oil-coating device 4 via oil supplying rolls 4b to enhance the release properties of the toner. Then, the unfixed toner image 3a is fixed on the printing sheet 3 by the fuser roll 1, and the fuser roll 1 rotates while carrying an unfixed toner thereon. The toner on the fuser roll 1 is removed by a cleaning sheet 5.
As above, the oil 4a is applied on the fuser roll 1 to remove the transferred toner. Therefore, not only the toner image 3b, but also the oil applied on the fuser roll 1 is transferred to the printing sheet 31. When the printing sheets 3, 31 are made of paper, and have a surface region not covered by the fixed toner, the oil is absorbed into such a surface region. Therefore, no major problem arises with respect to the oil transfer. However, when a whole surface of the printing sheet 3 is covered with the fixed toner, for example, where a photograph is reproduced by a color copying machine, or the like, the oil cannot be absorbed into the printing sheet surface that is entirely covered with the toner. Therefore, a problem arose in that uneven oil strips were formed on the fixed toner image, and thus the image quality was impaired. Further, when the printing sheet is made of a film having a poor absorbability of oil, the printing sheet cannot absorb the oil. Therefore, a problem arose in that the oil remained on the fixed toner image, and thus the image quality was impaired.
When an oil-coating device 4 as shown in FIG. 1 is used, the fuser roll 1 is coated with an oil, after the surface of the fuser roll 1 is wiped off by the cleaning sheet 5. A conventional cleaning sheet 5 is pressed onto the surface of the fuser roll 1 by a pinch roll 8 to remove the toner on the surface of the fuser roll 1, while the cleaning sheet is conveyed from a supplying shaft 6 around which the cleaning sheet 5 is wound, to a take-up shaft 7, in a direction of the arrow D as shown in FIG. 1, or in an opposite direction. When the toner is removed, however, there is a tendency for the oil to be unevenly removed from the fuser roll 1 by the cleaning sheet, and thus, as shown in FIG. 2, a residual oil layer 41 having an uneven thickness is formed on the surface of the fuser roll 1. Therefore, even if the oil is uniformly applied by the oil-coating device 4, a new oil layer 42 is formed, as shown in FIG. 3, in such a manner that the unevenness in the thickness of the residual oil layer 41 on the surface of the fuser roll 1 is aggravated. As a result, the oil is unevenly transferred onto the toner image fixed on the printing sheet, striped oil layers are formed, and thus the image quality is considerably impaired.
To remedy such defects, an attempt to uniformly remove the oil by strongly pressing the cleaning sheet 5 against the fuser roll 1 was made. However, there arose problems in that the fuser roll was easily damaged due to the strong pressure applied by the cleaning sheet 5, and thus the lifetime of the fuser roll 1 was shortened, or friction between the fuser roll 1 and the cleaning sheet 5 was increased, and thus mechanical vibration occurred.
Further, an attempt to reduce an amount of the oil applied from the oil-coating device 4 to the fuser roll 1 was conducted. However, the decrease in the amount of oil caused problems such that the release properties of the oil became worse, and off-set easily occurred.
Furthermore, instead of directly bringing the cleaning sheet 5 into contact with the fuser roll 1, an attempt to install a transfer roll capable of transferring the residual toner from the fuser roll 1, and bring the cleaning sheet 5 into contact with the transfer roll to thereby remove the residual toner and oil was made. However, it was impossible to completely remove the oil strips from the printing sheet.
Still further, a cleaning sheet containing an impregnated oil for removing a transferred toner from the fuser roll and applying the oil onto the fuser roll is known, as used in a fuser member, such as a fuser roll, in an electronic photography apparatus. In this case, however, a thickness of the oil applied on the fuser roll became uneven, and as a result, the oil was unevenly transferred onto the toner image fixed on the printing sheet, striped oil layers were formed, and thus the image quality was considerably impaired.
For example, Japanese Patent No. 2805221 discloses a cleaning sheet for a fuser roll in a copying machine, which comprises a thermally press-bonded nonwoven fabric sheet containing an impregnated silicone oil, and composed of ultrafinely divided fibers obtained from composite fibers having two or more resin components, and a radially cross-sectional shape, or of the above-mentioned ultrafinely divided fibers and thermoplastic fibers, wherein one of the divided fibers is a super-ultrafine fiber having a mostly triangular cross-sectional shape, and made of a heat-resistant resin component, such as 4-6-nylon, aromatic polyester, or aromatic polyamide. The cleaning sheet for a fuser roll can form a silicone oil layer on a fuser roll more uniformly than that formed by a conventional cleaning sheet. However, this was still insufficient.
An object of the present invention is to remedy the above defects. More particularly, the object of the present invention is to provide a cleaning sheet for a fuser member which can uniformly wipe off and remove an oil on a surface of the fuser member, and/or form an oil coating layer having an uniform thickness, without shortening a lifetime of the fuser member, such as a fuser roll, without causing mechanical vibration, or without impairing the release properties of toners, and to provide a supplier of the cleaning sheet for a fuser member, and a cleaning apparatus for a fuser member comprising the supplier.
Other objects and advantages will be clear from the following description.
According to the present invention, there is provided a cleaning sheet for a fuser member, comprising an ultrafine fibers-containing portion including (a) first ultrafine fibers (hereinafter sometimes referred to as the ultrafine fibers A) formed from a resin having a softening point of higher than 230xc2x0 C., having a non-circular cross-sectional shape, and having a fiber diameter of not more than 10 xcexcm, and (b) second ultrafine fibers (hereinafter sometimes referred to as the ultrafine fibers B) formed from a resin having a softening point of 150 to 230xc2x0 C., and having a fiber diameter of not more than 10 xcexcm, wherein at least one surface of the cleaning sheet is contained in the ultrafine fibers-containing portion, and the second ultrafine fibers in a surface portion containing the surface are deformed by press-attaching.
The cleaning sheet for a fuser member of the present invention has excellent properties for wiping off of a toner and an oil. This is believed to be because the cleaning sheet of the present invention contains the first ultrafine fibers, i.e., the ultrafine fibers A, in a surface to be brought into contact with the fuser member, such as a fuser roll, and the second ultrafine fibers, i.e., the ultrafine fibers B, are not fused, but deformed by press-attaching, namely, press-attachedly deformed. Further, the cleaning sheet of the present invention has a smooth surface, has a large area able to come into contact with the fuser member, such as a fuser roll, exhibits an excellent removability of an oil, and is capable of forming an oil layer having a uniform thickness. This is believed to be because the surface able to come into contact with the fuser member, such as a fuser roll, contains the ultrafine fibers B in the press-attachedly deformed state. Furthermore, the cleaning sheet of the present invention provides a far greater removability of the oil, and can form a more uniform oil layer, in comparison with conventional cleaning sheets. This is also believed to be because the ultrafine fibers B in the cleaning sheet of the present invention are softened when brought into contact with the fuser member, such as the fuser roll, having a surface temperature of about 150xc2x0 C. to 200xc2x0 C., and therefore, the cleaning sheet of the present invention can be deformed to fit the shape of the fuser member.
According to the cleaning sheet of the present invention, as above, the oil removal is excellent, an oil layer having a uniform thickness can be formed, a lifetime of a fuser member, such as a fuser roll, is not shortened or mechanical vibration does not occur because it is not necessary to strongly press the cleaning sheet against a fuser member, such as a fuser roll, and a release property of a toner is not impaired because it is not necessary to reduce an amount of oil coated on a fuser member, such as a fuser roll, only by making use of the cleaning sheet of the present invention used as a conventional cleaning sheet.
Further, the present invention relates to a supplier of a cleaning sheet for a fuser member, comprising the cleaning sheet, a supply shaft around which the cleaning sheet is wound from an end thereof, and a take-up shaft to which the other end of the cleaning sheet is fixed.
The cleaning sheet supplier will always bring a fresh surface of the cleaning sheet into contact with a surface of a fuser member, such as a fuser roll, and therefore, oil on the surface of the fuser member can be uniformly removed, and an oil layer with a uniform thickness can be formed.
Further, the present invention relates to a cleaning apparatus for a fuser member, comprising the supplier, a means for holding the supplier, a means for conveying the cleaning sheet of the supplier, and a means for pressing the cleaning sheet to a fuser member.
The cleaning apparatus of the present invention will always bring a fresh surface of the cleaning sheet into contact with a surface of a fuser member, such as a fuser roll, and therefore, oil on the surface of the fuser member can be uniformly removed, and an oil layer with a uniform thickness can be formed.